This invention relates to converters in general and more particularly to a conversion technique which is particularly applicable in obtaining a shaft angle to linear DC voltage conversion.
It is often necessary to translate a shaft angle position into a proportional DC voltage for use in DC servo loops, displays and so forth. Often a linear potentiometer is used. However, this approach suffers in high accuracy applications because of both the expense and the poor reliability of the device.
Another well known approach to the solution of this problem is the use of a linear synchro. Typically such synchros are excited with a 400 HZ sinusoidal waveform and the output of the synchro is demodulated using synchronous demodulation techniques in order to transform the resulting 400 HZ sinusoidal output into a required DC voltage. Typically, accuracies for such a synchro is 0.5% of full scale with the associated electronics typically causing another 0.1% error. Increasing the accuracy requires a large increase in the cost of both the wound component and the electronics.
Similar problems exist in other types of devices such as conventional synchros, resolvers and also in linear and rotary variable differential transformers.